The present invention relates to a system for automatically dimming vehicle high beam headlamps.
Regulations set forth by the United States Department of Transportation (DOT) regulate the light emissions of vehicle high beam headlamps. Various state regulations are used to control the amount of glare experienced by drivers of other vehicles whether the vehicle is traveling in the same direction as the controlled vehicle or in an opposite direction.
Known vehicle high beam headlamp emissions in accordance with the DOT regulations provide an intensity of 40,000 cd at 0 degrees, 10,000 cd at 3 degrees, 3250 cd at 6 degrees, 1500 cd at 9 degrees, and 750 cd at 12 degrees. An example of such an emission pattern is illustrated in FIG. 1. In order to avoid an illuminance of 0.5 foot candles (fc) incident on another vehicle, the vehicle high beam headlamps should be dimmed within 230 feet of another vehicle at 0 degrees, 115 feet of another vehicle at a horizontal position of 3 degrees relative to the datum, and 65 feet in the position of the other vehicle is 6 degrees relative to the controlled vehicle.
Various known head light dimmer control systems are known in the art. In order to prevent the drivers of other vehicles from being subjected to excessive glare levels, such automatic headlamp dimmer systems must sense both the head lights as well as the tail lights of other vehicles. While many known systems are adequately able to detect headlamps of oncoming vehicles, such systems are known to inadequately sense tail lights of vehicles traveling ahead of the control vehicle. As such, such systems are not able to automatically dim the high beam headlamps in time to prevent drivers of the vehicles traveling in the same direction as the controlled vehicle being subjected to excessive glare levels.
U.S. Pat. No. 5,537,003, assigned to the same assignee of the present invention, discloses an automatic headlamp dimming system which includes an optical system for sensing tail lamps as well as headlamps. The '003 patent discloses a single photo diode with a mechanical scanning arrangement for scanning a predetermined field of view. Although the system provides relatively suitable sensing of headlamps as well as tail lamps, the optical subsystem is rather complicated and expensive to manufacture.